The First Epistle of John, often referred to as First John and written 1 John, is a book of the New Testament. This fourth catholic or "general" epistle is attributed to John the Evangelist, traditionally thought to be the author of the Gospel of John and the other two Epistles of John.

This Epistle was written in Ephesus between the years 95-110. The work was written to counter docetism, the heresy that Jesus did not come "in the flesh," but only as a spirit. It also defined how Christians are to discern true teachers: by their ethics, their proclamation of Jesus in the flesh, and by their love. (Summary by Wikipedia)